The present invention is generally directed to a curable sealant composition. It is more specifically directed to a poly(conjugated diene) curable sealant composition.
Polymers, such as polyisobutylene, have found applications in building sealants due to inherent moisture impermeability. To function as a sealant, a curable group is usually combined with the isobutylene units, resulting in, for example, alkoxy-silane functionalized polyisobutylene. Current polyisobutylene building sealants are often formed using a two-step process. The polymer backbone is formed and endcapped with a reactive functional group. The reactive functional group is then reacted, often in the presence of a metal catalyst, resulting in the presence of a curable group on the polymer backbone. In one specific example, the polymer is endcapped with allyl groups through the use of allyltrimethylsilane. Then, the allyl group is hydrosilylated using a platinum catalyst and an appropriate silane. In another method, the reactive functional groups are dispersed throughout the polymer backbone, followed by the reaction of the functional groups to form curable siloxane groups within the polymer backbone. This two-step process is both expensive and cumbersome.
Accordingly, polyisobutylene-based sealants may suffer from several drawbacks. Moreover, such sealants are (i) often expensive to prepare and (ii) strongly influenced by the relatively high cost of isobutylene monomer. Furthermore, they are often limited to use as a two-part building sealant, requiring combination of the sealant with a catalyst immediately prior to use. If the catalyst is added to the sealant too soon, premature curing may occur, resulting in difficult, and inconsistent, application of the sealant. The requirement for end-user mixing may also result in inconsistencies in the building sealants due to carelessness on the part of the end-user.
It would be desirable to have available a less expensive, more efficient process to directly prepare alkoxysilane functionalized sealant compositions with low polydispersity.